31P magnetic resonance spectroscopy can be used to estimate the time of death in humans, based on the ratio of ATP to inorganic phosphate, which falls exponentially for up to 8 hours post-mortem.

This is the conclusion of researchers in Germany and the USA, who admit that it might not be widely adopted. “Compared to the measurement of the body core temperature which is the current gold standard for estimating the time of death postmortem MRS has several disadvantages.” These include the cost of the equipment and the technical support required. However, some forensic institutes use magnetic resonance imaging for examining soft tissue damage, so the future might not be so bleak.

Writing in Forensic Science International, they describe how the ratio of the signals originating from alpha-ATP and inorganic phosphate falls after an initial period, reducing from 0.445 to 0.032 during the first 24 hours after death. An inverse log function of the ratio allowed the post-mortem interval to be determined with 95% confidence.

The conventional way to estimate time of death is from the core body temperature, measured with a rectal thermometer. This is affected by external factors like temperature and must be correlated with the weight of the corpse. However, the effects of temperature on the MRS results also need to be tested and the size of the study needs to be enlarged to substantiate the results: only eight corpses were studied here.